Chapter 12 Calling EAServer Component Methods from PowerDynamo

What does EAServer bring to PowerDynamo applications?

EAServer is a platform-independent component transaction server that allows you to develop component-based applications that can be accessed by thousands of clients simultaneously. EAServer brings flexibility to PowerDynamo scripts by allowing you to create a component, deploy it to the EAServer, and share it among remote sites using PowerDynamo scripts that call the EAServer component.

PowerDynamo also brings flexibility to EAServer by providing a means for accessing EAServer components and their business logic through an ultra-thin intranet or Internet client.

The benefits of using EAServer components with PowerDynamo

EAServer components can be:

Java/Enterprise JavaBeans
CORBA C++
ActiveX (nonvisual)
C
PowerBuilder NVO

You can call these components from within a Dynamo script as stored procedures or as ActiveX or Java objects. The type of component being accessed is irrelevant to the client.

The main benefits to using EAServer components in Dynamo scripts include:

Business logic stored in one EAServer component becomes available to many presentation-independent clients.
EAServer makes powerful native code components such as C and C++ available for execution by Dynamo scripts that would otherwise not have access to methods written in those languages. There are few limitations on the languages Dynamo scripts can use.
Components can be updated in one location. Without EAServer, changes to a component or a stored procedure would be required at each client. Setting up Dynamo to access EAServer components can be as simple as creating a connection to the EAServer or installing the ActiveX proxy server.

The way that EAServer components are accessible by Dynamo is advantageous because there are no restrictions on how Dynamo can manipulate the component results. The component results, in the form of HTML pages, are controlled by Dynamo.

A brief summary on setting up clients to access EAServer is given in the next section. For detailed information on setting up clients that require EAServer access, see the EAServer Programmer's Guide.

MASP method calls versus ActiveX or Java objects

There are a few benefits to using ActiveX or Java objects against an EAServer component instead of MASP method calls:

ActiveX or Java objects exist until they go out of scope, whereas MASP calls create an instance of the component, execute it, and destroy it immediately.
ActiveX or Java objects can give any type of return. MASP calls, from PowerDynamo, can return only a result set.
ActiveX or Java objects are treated like normal DynaScript objects, while MASP calls (except the connection.CreateComponent method) require that you enter a full string each time you make a call.

If a script requires repeated use of an EAServer component, creating an ActiveX object or Java stub is the preferred method of working with an EAServer component and its methods. ActiveX, however, is a Microsoft technology, which means it is only available on Microsoft operating systems. Java, on the other hand, is platform-independent, which means that Java objects can run anywhere.